The present invention relates to a solar radiation collector of the type composed of a mat formed of a black foil member and a radiation pervious foil member, the two members being connected together along the outer edges of the mat and at interior locations of the mat to form an inlet and outlet and an extended flow path for a fluid heat carrier medium between the inlet and outlet, the collector further including a cover connected to the mat along opposed edges thereof and arranged to be disposed in the path of solar radiation toward the mat with an air space being defined between the mat and the cover, with the connections at interior locations of the mat serving to form parallel flow channels defining portions of the flow path and extending parallel to the opposed edges of the mat along which the cover is connected such that the dimension of the mat between the opposed edges at which the cover is connected has a first value when the mat does not contain heat carrier medium and is in a flattened state and a second value less than the first value when the mat is filled with heat carrier medium and is thus in an inflated state.
Solar radiation collectors of this type, which have the advantage of being collapsible or rollable for transport, are disclosed in U.S. Pat. No. 4,059,095, and are composed of a mat which includes when viewed in the direction toward the radiation source, a lower, black foil member, and an upper, transparent, or radiation pervious, foil member, associated with a further transparent, or radiation pervious foil member which constitutes a cover and which is welded to the mat at those points at which the two foil members forming the mat are connected together. Between the mat on the one hand and the further transparent foil member forming the cover on the other hand, there are created heat insulating chambers filled with air.